Disposable antifouling covers for geophysical survey equipment

ABSTRACT

Disposable antifouling covers for geophysical survey equipment. At least of example embodiments are methods including deploying marine geophysical survey equipment. The deploying may include: installing a disposable antifouling cover of plastic material on a portion of the marine geophysical survey equipment, wherein the disposable antifouling cover occludes a majority of an exterior surface of the portion of the marine geophysical survey equipment; and placing the marine geophysical survey equipment in a body of water.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. App. No. 14/031,059filed Sep. 19, 2013 titled “Disposable Antifouling Covers forGeophysical Survey Equipment” (now U.S. Pat. No. 9,465,127). The Ser.No. 14/031,059 application claimed the benefit of U.S. ProvisionalApplication Ser. No. 61/820,639 filed May 7, 2013and titled “DisposableAntifouling Covers.” Both applications are incorporated by referenceherein as if reproduced in full below.

BACKGROUND

Geophysical surveying (e.g., seismic, electromagnetic) is a techniquewhere two- or three-dimensional “pictures” of the state of anunderground formation are taken. Geophysical surveying takes place notonly on land, but also in marine environments (e.g., ocean, largelakes). Marine geophysical survey systems frequently use a plurality ofsensor streamers (long cables), which contain one or more sensors todetect energy emitted by one or more sources. Some marine geophysicalsurvey systems include cables or nodes secured at the bottom of themarine environment. Deployment of sensor streamers and sources oftenutilizes additional equipment, such as paravanes, lead cables, andlateral or depth control devices.

Any equipment that operates in water, particularly equipment thatoperates in the ocean in warm equatorial environments, is subject tofouling by various sea creatures, such as barnacles, mussels, oysters,algae, tubeworms, and bacterial slime (collectively referred to as“marine growth”). Marine growth increases weight of equipment, and alsoincreases drag. The additional weight and increased drag may increasefuel cost to tow the equipment through the water, and in some cases mayinterfere with operation of the equipment itself.

BRIEF DESCRIPTION OF THE DRAWINGS

For a detailed description of exemplary embodiments, reference will nowbe made to the accompanying drawings in which:

FIG. 1 shows an overhead view of a marine survey system in accordancewith at least some embodiments;

FIG. 2 shows a perspective view of a streamer positioning device inaccordance with at least some embodiments;

FIG. 3 shows a perspective view of an antifouling cover in accordancewith at least some embodiments;

FIG. 4 shows a cross-sectional elevation view of the antifouling covertaken substantially along lines 4-4 of FIG. 3;

FIG. 5 shows a perspective view a portion of an antifouling cover inaccordance with at least some embodiments;

FIG. 6A shows a cross-sectional elevation view of an antifouling coverand a wing during installation of an antifouling cover, in accordancewith at least some embodiments;

FIG. 6B shows a cross-sectional elevation view of an antifouling coverand a wing once the antifouling cover has been fully telescoped over thewing, in accordance with at least some embodiments;

FIG. 7 shows a perspective view of a streamer positioning device inaccordance with at least some embodiments;

FIG. 8 shows a perspective view a portion of an antifouling cover inaccordance with at least some embodiments;

FIG. 9 shows a perspective view a portion of an antifouling cover inaccordance with at least some embodiments;

FIG. 10 shows a perspective, partial cut-away, view of wing with a coversystem in accordance with at least some embodiments;

FIG. 11 shows a block diagram of a method in accordance with at leastsome embodiments; and

FIG. 12 shows a block diagram of a method in accordance with at leastsome embodiments.

NOTATION AND NOMENCLATURE

Certain terms are used throughout the following description and claimsto refer to particular system components. As one skilled in the art willappreciate, different companies may refer to a component by differentnames. This document does not intend to distinguish between componentsthat differ in name but not function. In the following discussion and inthe claims, the terms “including” and “comprising” are used in anopen-ended fashion, and thus should be interpreted to mean “including,but not limited to . . . .” Also, the term “couple” or “couples” isintended to mean either an indirect or direct connection. Thus, if afirst device couples to a second device, that connection may be througha direct connection or through an indirect connection via other devicesand connections.

“Cable” shall mean a flexible, load carrying member that also compriseselectrical conductors and/or optical conductors for carrying electricalpower and/or signals between components.

“Rope” shall mean a flexible, axial load carrying member that does notinclude electrical and/or optical conductors. Such a rope may be madefrom fiber, steel, other high strength material, chain, or combinationsof such materials.

“Line” shall mean either a rope or a cable.

“Plastic material” shall mean materials comprising organic polymers,including thermoplastics and thermosetting polymers.

“Chord line” shall mean an imaginary straight line connecting theleading and trailing edges of an object at a particular cross-section ofthe object.

“Leading edge” shall mean a portion of a piece of equipment that, duringtowing of the equipment through water during a marine geophysicalsurvey, is the leading portion along the towing direction.

“Latching force” shall mean a force tending to hold two devices in anabutting relationship.

“Marine geophysical survey equipment” shall mean equipment deployed ortowed in a body of water during a geophysical survey (e.g., seismic,electromagnetic) of underground formations.

“Disposable cover” and “disposable antifouling cover” shall mean adevice that covers or occludes a portion of marine geophysical surveyequipment, where the useful life of the disposable cover is less thanhalf the expected useful life of the portion of the marine geophysicalsurvey equipment covered.

DETAILED DESCRIPTION

The following discussion is directed to various embodiments of theinvention. Although one or more of these embodiments may be preferred,the embodiments disclosed should not be interpreted, or otherwise used,as limiting the scope of the disclosure or the claims. In addition, oneskilled in the art will understand that the following description hasbroad application, and the discussion of any embodiment is meant only tobe exemplary of that embodiment, and not intended to intimate that thescope of the disclosure or the claims, is limited to that embodiment.

The various embodiments are directed to disposable antifouling coversfor marine geophysical survey equipment, also referred to herein as“marine geophysical survey devices”, or simply “devices”. “Disposable”in this context means that the cover has a “limited use”, a “limitedlife”, or may be for “single use.” That is, a disposable antifoulingcover in accordance with the various embodiments is designed andconstructed to be used for number of operating hours N, where N is halfor less of the number of hours of expected useful life of the portion ofthe marine geophysical survey equipment covered. Stated alternately, adisposable cover in accordance with various embodiments is designed andconstructed such that the cover would not be expected to withstandremoval of marine growth from the cover by mechanical means (e.g., powerwashing, sand blasting); rather, the cover would be disposed of ordiscarded rather than cleaned. Such a disposable cover would be expectedto recognize benefits of single use materials, such as costs savings andweight savings (which translate into drag reduction).

The various embodiments were developed in the context of disposableantifouling covers used on the wings of streamer positioning devices,the antifouling covers used to reduce marine growth on the wings. Theexample embodiments discussed below are based on the developmentalcontext; however, the developmental context shall not be read to limitthe applicability of the methods and systems described. One of ordinaryskill, after having read and understood the various embodimentsdiscussed herein, could extend the teachings to other marine geophysicalsurvey equipment. The specification first turns to a description of anexample marine surveying system.

FIG. 1 shows an overhead view of a marine survey system 100 inaccordance with at least some embodiments. In particular, FIG. 1 shows asurvey vessel 102 having onboard equipment 104, such as navigation,energy source control, and data recording equipment. Survey vessel 102is configured to tow one or more streamers 106A-F through the water.While FIG. 1 illustratively shows six streamers 106, any number ofstreamers 106 may be used. The discussion continues with respect tostreamers 106 being sensor streamers, but (for the purpose of thisdisclosure) streamers 106 are illustrative of any towed geophysicalsurvey cable whether or not the towed geophysical cable is associatedwith spread line (e.g., transmitter cables, and source cables).

The sensor streamers 106 are coupled to towing equipment that maintainsthe sensor streamers 106 at selected lateral positions with respect toeach other and with respect to the survey vessel 102. The towingequipment may comprise two paravane tow lines 108A and 1086 each coupledto the vessel 102 by way of winches 110A and 1106, respectively. Thewinches enable changing the deployed length of each paravane tow line108. The second end of paravane tow line 108A is coupled to a paravane112, and the second end of paravane tow line 1086 is coupled to paravane114. In each case, the tow lines 108A and 108B couple to theirrespective paravanes through respective sets of lines called a “bridle”.The paravanes 112 and 114 are each configured to provide a lateral forcecomponent to the various elements of the survey system when theparavanes are towed in the water. The combined lateral forces of theparavanes 112 and 114 separate the paravanes from each other until theparavanes put one or more spreader lines 120, coupled between theparavanes 112 and 114, into tension. The paravanes 112 and 114 eithercouple directly to the spreader line 120 or as illustrated couple to thespreader line by way of spur lines 122A and 122B.

The sensor streamers 106 are each coupled, at the ends nearest thevessel 102 (i.e., the proximal ends) to a respective lead-in cabletermination 124A-F. The lead-in cable terminations 124 are coupled to orare associated with the spreader lines 120 so as to control the lateralpositions of the streamers 106 with respect to each other and withrespect to the vessel 102. Electrical and/or optical connections betweenthe appropriate components in the recording system 104 and the sensors(e.g., 116A, 116B) in the streamers 106 may be made using lead-in cables126A-F. Much like the tow lines 108 associated with respective winches110, each of the lead-in cables 126 may be deployed by a respectivewinch or similar spooling device such that the deployed length of eachlead-in cable 126 can be changed.

Still referring to FIG. 1, in many cases the sensor streamers 106 willbe associated with a plurality of streamer positioning devices. Forexample, the sensor streamers 106A-F may be associated with streamerpositioning devices 150A-F, respectively, shown coupled on proximal endof the sensor streamers. In many cases, the streamer positioning devices150A-F may provide only depth control, as the lateral spacing of thesensor streamers near the proximal ends may be adequately controlled bythe spreader cable 120, and twisting (i.e., rotation about the long axisof the sensor streamer) may not be an issue close to the lead-in cableterminations 124A-F. Further, the sensor streamers 106A-F may beassociated with streamer positioning devices 152A-F, respectively, showncoupled further from the proximal ends, and in some cases near thedistal ends of the sensor streamers 106A-F. The streamer positioningdevices 152A-F may provide not only depth control, but also lateralpositional control and may assist in preventing twisting experienced bythe sensor streamers. In some cases each sensor streamer 106 may be 1000to 10000 meters in length, and may comprise 20 or more streamerpositioning devices.

FIG. 2 shows a streamer positioning device 200 in accordance with atleast some embodiments. Streamer positioning device 200 may beillustrative of either streamer positioning device 150A-F or 152A-F, andmay be, for example EBIRD® wings available from Kongsberg Maritime AS,Kongsberg Norway. The streamer positioning device 200 comprises aplurality of wings 202 arranged about and extending radially outwardfrom a central chassis 201, which central chassis is designed to couplein series with a sensor streamer 106. The example streamer positioningdevice 200 is designed to control lateral, vertical, and rotationalmovement of the sensor streamer 106 by selectively articulating eachwing 202 about a respective articulation axis. For streamer positioningdevices designed only for depth control, two wings may be used where thewings articulate in unison to provide forces to control or maintain aparticular depth. The outer skin 204 of each wing may be secured to awing sub-chassis (not visible) by one or more fasteners 206, whichfasteners may comprise screws, bolts, rivets, or other such fasteningdevices. Only a small number of fasteners 206 associated with a singlewing are shown so as not to unduly complicate the figure; however, eachwing may comprise respective fasteners that couple the outer skin to theunderlying wing sub-chassis. Each wing 202 comprises a proximal end 208close to the central chassis 201, and a distal end 210 opposite theproximal end 208. Moreover, each wing may define a cross-sectional shape(taken along a direction of towing) of a symmetrical airfoil, and thuseach wing also defines a leading edge 214 and a trailing edge 216.

Each wing comprises an outer surface 212, and the outer surface 212 maybe prone to hosting marine growth (e.g., barnacles), particularly on andaround the fasteners 206. The marine growth not only adds mass to thewings, but also increases drag and may interfere with articulation ofthe wings to implement streamer position control. Many sensor streamers106 may be towed behind a single survey vessel 102, and each sensorstreamer 106 may have a plurality of streamer positioning devices, suchas devices 150 and 152. The process of removing marine growth from thewings 202 (e.g., power washing, sand blasting) of a correspondinglylarge number of streamer positioning devices 200 may be bothtime-consuming and costly.

FIG. 3 shows a perspective view of a disposable antifouling cover 300(hereafter just “antifouling cover 300”) in accordance with exampleembodiments. In particular, the example antifouling cover 300 comprisesan elongate body 302 shaped to telescope over and occlude a wing 202 ofa streamer positioning device, such as shown in FIG. 2. Thus, theantifouling cover 300 defines an exterior surface 304, an interiorsurface 306, and an interior volume 308. Much like the wing 202 overwhich the antifouling cover 300 telescopes, the elongate body defines aproximal end 310, a distal end 312, a leading edge 314, and a trailingedge 316. In many cases, and as shown, the proximal end 310 defines anaperture 317 into the interior volume 308, while the distal end isclosed (and thus may be referred to as closed distal end). When the wing202 over which the antifouling cover 300 will telescope has across-sectional shape of a symmetric airfoil, the interior volume 308will likewise define a symmetric airfoil. In most cases the outersurface 304 will also define a complementary symmetric airfoil when theinterior volume 308 defines a symmetric airfoil, but interiorcross-section and the exterior cross-section need not correspond inevery case.

In accordance with example embodiments, the elongate outer body 302 mayalso define one or more latching features proximate the aperture 317,with the one or more latching features providing a latching force tohold the antifouling cover 300 on the wing 202 when the antifoulingcover 300 is telescoped over the wing 202. In the example antifoulingcover of FIG. 3, the one or more latching features comprise a firstflange member 320 and a second flange member 322. Each flange member isa portion of the material of the elongate body 302 that is bent orformed to protrude inward relative to the aperture 317. The flangemember as a feature providing a latching force is discussed more after adiscussion of FIG. 4 regarding terms related to the cross-sectionalshape of the antifouling cover 300. In some embodiments, a latchingforce may be provided or supplemented by static electricity, magnetic,vacuum, or chemical bonding forces.

FIG. 4 shows a cross-sectional elevation view of an example antifoulingcover 300 taken substantially along line 4-4 of FIG. 3. Thecross-sectional view is at the aperture 317, and thus the flange members320 and 322 are cut away and not visible, but the balance of theproximal end 310 of the example antifouling cover is visible. Inparticular, the aperture 317 defines a plane, which in FIG. 4corresponds to the plane of the page. A chord line 400 may beconceptually defined, where the chord line resides in the plane definedby the aperture, and where the chord line spans the inside surface 306between the leading edge 314 and the trailing edge 316. The chord linehas a length, and the length may thus be referred to as a chord length.Further, an interior dimension 402 may be defined, where the interiordimension may be measured perpendicular to the chord line 400 and alongthe plane defined by the aperture 316. In some cases the largestinterior dimension may be of interest. The chord length is greater thanthe largest interior dimension 400, in some cases the chord length ismore than twice the largest interior dimension 400, and in yet stillfurther cases the chord length is more than four times the largestinterior dimension 400.

Returning to FIG. 3, the example latching features in the form of flangemembers 320 and 322 are shown positioned not only at the aperture 317and protruding inward toward the chord line (not expressly shown in FIG.3), but in the particular case of FIG. 3 the flange members 320 and 322intersect the largest interior dimension 402 (not expressly shown inFIG. 3). FIG. 5, however, shows a perspective view of the proximal end310 of an antifouling cover 300 in accordance with another exampleembodiment. In particular, the antifouling cover 300 of FIG. 5 comprisesa latching feature in the form of the flange member 500, where theflange member 500 is likewise disposed at the aperture 317, but in thiscase the flange member 500 is disposed at the intersection of the chordline and the leading edge 314. While FIG. 5 shows the flange member 500used alone, in other cases the flange member 500 may be used inconjunction with one or both of flange member 320 and 322. Beforeproceeding, it is noted that the flange members 320 and 322 are shown assmoothly varying surfaces to create the inward protrusion, while flangemember 500 is shown as a sharp, right angle to create the inwardprotrusion; however, any inward protruding member, regardless of howsmooth or sharp the transition from the outer surface 304 of theelongate body 302 to the inward protrusion, is contemplated.

FIGS. 6A and 6B each show a cross-sectional elevation view of a portionof an antifouling cover 300 telescoped over a wing 202, in each casewhere flange members are used to provide a latch force to hold theantifouling covers 300 on the wing 202 during use. In particular, FIG.6A shows a portion of the elongate body 302 partially telescoped over awing 202. FIG. 6A also shows first flange member 320 and second flangemember 322. As the elongate body 302 telescopes onto the wing 202 (inthe direction shown by arrow 600), the flange members 320 and 322 arebias outwardly (i.e., away from the internal volume of the antifoulingcover 300). However, and now referring to FIG. 6B, once the elongatebody 302 telescopes sufficiently onto the wing 202, the bias on theflange members 320 and 322 is released as the flange members 320 and 322“snap” over the proximal end 208. The flange members 320 and 322 providea latching force to hold the antifouling cover on the wing. Theprinciple of operation is equally applicable to flange member 500, andso as not to further complicate the specification the biased andnon-biased orientation of flange member 500 is not expressly shown.Finally, while separate flange members 320, 322, and 500 are shown anddiscussed, in yet still other example embodiments a single flange memberprotruding inward may fully circumscribe the proximal end of theelongate body 302.

FIG. 7 shows a perspective view of a streamer positioning device 200 inaccordance with yet still further example embodiments. In particular,the wings 202 of the streamer positioning device 200 of FIG. 7 comprisefurther example features that may assist in providing a latching forcefor antifouling covers placed over the wings 202. Wing 202A shows afeature in the form of a trough 700 formed in the outer surface 204 ofthe wing 202, and as shown the trough may circumscribe the entire wing202A. The size and depth of the trough is exaggerated in FIG. 7 forpurposes of clarity. The trough defines a direction that is parallel toa tow direction of the streamer positioning device 200, the towdirection shown by arrow 702. In practice, the depth of the exampletrough may be a centimeter or less, and in many case three millimetersor less. In other cases, the trough may have a length that less thancircumscribes the entire wing 202A (e.g., half way around and includingthe leading edge 214). In most cases the trough 700 will be near theproximal end 208 of the wing 202A (e.g., within 5 centimeters), butother locations are also contemplated.

FIG. 8 shows a perspective view of an antifouling cover 300 that worksin conjunction with the trough 700. In particular, FIG. 8 shows theelongate outer body 302, aperture 317, and the interior surface 306.Defined on the interior surface 306 is a ridge member 800 having itsbase on the interior surface 306, and ridge extending inward from theinterior surface. Considering together the wing 202A of FIG. 7 and theantifouling cover 300 of the FIG. 8, when the antifouling cover 300 istelescoped over the wing 202A, the ridge 800 snaps into and mates withthe trough 700. When the ridge 800 and trough 700 are in an abuttingrelationship, the ridge 800 and trough 700 provide a force tending toresist movement of the antifouling cover off the wing 202A.

Returning to FIG. 7, FIG. 7 further shows another example feature on thewing that may assist in providing a latching force for antifoulingcovers. In particular, wing 202B shows a series of indentions 704 formedin the outer surface 204 of the wing 202B. The size and depth of theindentions 704 is exaggerated in FIG. 7 for purposes of clarity. Theexample indentions may be aligned in a direction that is parallel to atow direction (again arrow 702) of the streamer positioning device 200.In practice, the depth of each example indention may be a centimeter orless, and in many case three millimeters or less. In most cases theindentions 704 will be near the proximal end 208 of the wing 202B (e.g.,within 5 centimeters), but other locations are also contemplated.

FIG. 9 shows a perspective view of an antifouling cover 300 that worksin conjunction with the indentions 704. In particular, FIG. 9 shows theelongate body 302, aperture 316, and the interior surface 306. Definedon the interior surface 306 are a plurality of protrusion members 900,each protrusion member having its base on the interior surface 306 andextending inward from the interior surface. Considering together thewing 202B of FIG. 7 and the antifouling cover 300 the FIG. 9, when theantifouling cover 300 is telescoped over the wing 202B, the protrusions900 snap into and mate with the respective indentions 704. When theprotrusions 900 and indentions 704 are in respective matingrelationships, the protrusions 900 and indentions 704 provide a forcetending to resist movement of the antifouling cover off the wing 202B.

Before proceeding, it is noted that with respect to FIG. 7, thediffering features on wings would likely not be implemented in practice;rather, FIG. 7 is provided as a discussion tool to introduce variousfeatures on the wings and antifouling covers that may work together toprovide the latching force. In most cases, each wing of a streamerpositioning device would be identical, and thus too the antifoulingcovers would be identical and usable with any wing on a streamerpositioning device, and likewise every streamer positioning device ofthe same type within the entire set of marine geophysical surveyequipment.

In order to be installed over and at least partially occlude a wing of apositioning device, the interior surface of an antifouling may definethe negative image of the wing. In some cases, the elongate body 302,and in particular the outer surface 304, has a complementarycross-sectional shape that matches the cross-sectional shape of theinterior surface. Stated otherwise, in the example situation theinterior surface may define a negative image of the underlying device,and the outer surface may define “positive” or duplicate image of theunderlying device. Thus, because of the symmetry between the inner andouter shapes, a number of the antifouling covers 300 may be “stacked”together in an abutting relationship to reduce the space needed to storeand transport a large number of antifouling covers. In the example caseof antifouling covers 302 for wings of a positioning device, the coversmay be “stacked” by telescoping a plurality of antifouling coverstogether.

The example antifouling covers may be manufactured from any suitableneutrally- or positively-buoyant material. For example, the antifoulingcovers may be made from plastic materials such as high-densitypolyethylene (HDPE), low-density polyethylene (LDPE), polyethyleneterephthalate (PET), and other similar materials. In some cases, theantifouling covers may be manufactured using a vacuum forming method toreduce cost and enable large-scale production. In other cases, theantifouling covers may be made by injection molding processes. When madefrom a plastic material, the elongate outer body (e.g., elongate outerbody 302) may have a thickness T (FIG. 4) of one millimeter or less. Inyet still further cases, the antifouling covers may be made from anegatively-buoyant material such as aluminum or titanium.

In another embodiment, the example antifouling cover 300 may comprise adeformable or shrinkable section such that the antifouling cover 300(when installed over a wing) engages the wing 202 with sufficientfriction to prevent the antifouling cover 300 from becoming decoupledfrom the wing 202 as a result of hydrodynamic drag caused by towing thestreamer positioning device 200 through a marine environment.Deformability may take many forms. For example, the deformable sectionmay be activated by heat or electromagnetic radiation (e.g., ultravioletlight). In other cases, the deformable section may be activated byapplication of a chemical which invokes a chemical reaction that shrinksthe deformable section. In still other cases, the deformable section maycoincide with the location of flanges 320, 322, or 500, or may coincidewith the location of the ridge 800 or protrusions 900, such that oncethe example feature are interlocked with the wing 202 by deformation,further latch force may be created by shrinking the antifouling cover inplace at the location of the features.

In some embodiments, the exterior surface 304 conforms to the interiorsurface 306 of the antifouling cover 300 such that any indentionspresenting the outer skin 204 of the wing 202 would be evident on theexterior surface 306 of the antifouling cover 300. The presence of suchindention in the outer surface 306 matching indention in the outer skin204 might be particularly prevalent in cases where the antifouling cover300 is deformable as discussed in the immediately preceding paragraph.

Prior to use of the example streamer positioning device 200, anantifouling cover may be placed on each wing 202. The streamerpositioning device may be thereafter used in a marine environment withthe marine growth occurring on the antifouling cover 300 rather than theouter surface 212 of the wings 202. When the volume of marine growth onthe antifouling cover reaches a certain point (e.g., volume of marinegrowth, mass of marine growth, amount of additional drag created by themarine growth), the antifouling cover 300 may be easily removed by anoperator and replaced with a new antifouling cover 300. Thus,antifouling cover 300 reduces the cost and complexity of removing marinegrowth from streamer positioning devices 200.

Additionally, while the ease of removal, disposability, and/orrecyclable nature of the antifouling covers reduce the cost andcomplexity of removing marine growth from marine geophysical surveyequipment, the antifouling covers themselves may be designed to be moreresistant to marine growth or build-up. In particular, marine growth ismore prevalent in areas where a high amount of turbulence is present.Thus, in at least some embodiments, the exterior surface of the exampleantifouling cover 300 designed to reduce turbulence. In someembodiments, the exterior surface of the example antifouling cover 300may be substantially smooth. In some cases, substantially smooth mayrefer to a surface having features no larger than 1 millimeter,one-tenth of 1 millimeter, or one-hundredth of 1 millimeter. In otherembodiments, the exterior surface of the antifouling cover 300 comprisesa micro-texture designed to reduce hydrodynamic drag (e.g., riblets,dimples, or a “shark skin” pattern). Antifouling covers so designed maybe less susceptible to marine growth because of the substantially smoothouter surface and also reduces marine growth marine geophysical surveyequipment by occluding the fasteners and other textured surfaces.

Further, in some embodiments, a treatment may be applied to theantifouling covers to further reduce the chances of marine growth orbuild up. For example, a special antifouling coating (e.g., a paintcontaining copper powder) may be applied to the exterior of theantifouling covers. In some cases, the antifouling coating may beapplied to the antifouling covers just before or just after theantifouling covers are installed on the marine geophysical equipment.However, in other cases the antifouling coating may be applied well inadvance, such as when the antifouling covers are manufactured.Alternately or additionally, an antifouling agent may be included in thematerial (e.g., HDPE) from which the antifouling cover 300 ismanufactured. In this way, marine growth on the surface of theantifouling cover 300 is further limited.

In yet still other example embodiments, multiple antifouling covers maybe used with the single piece of marine geophysical survey equipment.FIG. 10 shows a perspective, partial cut-away, view of wing inaccordance with the further example embodiments. In particular, FIG. 10shows a wing 1000 (and only a portion of the outer skin 1002 isvisible). Telescoped over the wing 1000 is a first antifouling cover1004. The first antifouling cover may couple to the wing 1000 by way ofany mechanism previously discussed. Moreover, the example system furthercomprises a second antifouling 1006 telescoped over the firstantifouling cover 1004 (and thus telescoped over the wing 1000). Thesecond antifouling cover 1006 may couple to the underlying antifoulingcover 1004 (and thus the wing 1000) by way of any mechanism previouslydiscussed. Thus, the first and second antifouling covers may beconsidered a cover system 1008, and while two antifouling covers 1004and 1006 are expressly discussed as part of the cover system 1008, twoor more antifouling convers may be used in the cover system 1008. Insome cases no more than three antifouling covers may be initiallyimplemented in the cover system 1008.

The example antifouling covers 1004 and 1006 may be installedsequentially (first the antifouling cover 1004, and then the antifoulingcover 1006), or the antifouling covers may be simultaneously telescopedover the wing 1000. In the simultaneous case, the second antifoulingcover 1006 may be telescoped over the first antifouling cover 1004 inadvance of the installation (e.g., during manufacturing, on thedeployment vessel). In the example cover system 1008, each antifoulingcover may be slightly larger than the antifouling cover beneath, suchthat each successive outer antifouling cover fully occludes theantifouling cover beneath. In other cases, the antifouling covers may bestructurally the same size, and thus while each successive outerantifouling cover may substantially occlude the under the antifoulingcover, slight exposure of the underlying cover is possible. Thus, thecover system 1008 may have stacked configuration similar to the stackedconfiguration for storage and transportation discussed above.

In operation, the cover system 108 may be used within a marinegeophysical survey, and when the marine growth on the outermostantifouling cover exceeds a predetermined threshold, then the outermostantifouling cover may be removed (e.g., by a work boat while thepositioning device is still in the water), thus exposing the nextunderlying antifouling cover.

FIG. 11 shows a method in accordance with example embodiments. Inparticular, the method starts (block 1100) and comprises deployingmarine geophysical survey equipment (block 1102). The deploying maycomprise: installing a disposable antifouling cover of plastic materialon a portion of the marine geophysical survey equipment, wherein thedisposable cover occludes a majority of an exterior surface of theportion of the marine geophysical survey equipment (block 1104); andplacing the marine geophysical survey equipment in a body of water(block 1106). That is, in some cases the disposable covers of plasticmaterial may be installed before placing marine geophysical surveyequipment in the water. In other cases, the disposable covers of plasticmaterial may be installed after the marine geophysical survey equipmentis already in the water, the installation by separate work boat, forexample. In some embodiments, deploying may also comprise applying atreatment to the disposable cover to further reduce the chances ofmarine growth or build up. The example method may further include towingthe marine geophysical survey equipment (block 1008). In some cases, themarine geophysical survey equipment will be secured at a location in thebody of water. Thereafter, the method ends (block 1110).

FIG. 12 shows a method in accordance with further embodiments. Inparticular, the method starts (block 1200) and comprises retrievingmarine geophysical survey equipment, wherein a portion of the marinegeophysical survey equipment is covered by a disposable antifoulingcover (block 1202). The retrieving may comprise: extracting the marinegeophysical survey equipment from a body of water (block 1204); andremoving the disposable cover (block 1206). Removing the cover (againblock 1206) may take place on the deck of vessel retrieving the marinegeophysical survey equipment. In other cases, the removing of the covermay take place while the marine geophysical survey equipment, or portionthereof, is still in the water, for example, by way of a work boat,where the work boat is distinct from the vessel onto which the marinegeophysical survey equipment is retrieved. Moreover, removing maycomprise dislodging any of a plurality of features of the disposablecover. For example, dislodging may comprise dislodging a flange member,dislodging a protrusion defined on an interior surface of the cover, ordislodging a ridge defined on an interior surface of the cover. In thecase of a shrinkable portion of the disposable antifouling cover,removing may comprise cutting, ripping, unwrapping, chemical peel, airinjection, or expansion. Moreover, in most cases the retrieving step isrepeated for portion of the marine geophysical survey equipment on whicha disposable cover has been placed. Thereafter, the method ends (block1208).

In some embodiments, the methods of FIGS. 11 and 12 may be combined. Forexample, when multiple antifouling covers are used with the single pieceof marine geophysical survey equipment, removal of an outer-most covermay be immediately followed by re-deployment of the marine geophysicalsurvey equipment. Removal of the outer-most cover might also beimmediately followed application of a treatment to the next-outer-mostcover to further reduce the chances of marine growth or build up, andthen subsequently followed by re-deployment of the marine geophysicalsurvey equipment.

References to “one embodiment,” “an embodiment,” “a particularembodiment,” and “some embodiments” indicate that a particular elementor characteristic is included in at least one embodiment of theinvention. Although the phrases “in one embodiment,” “an embodiment,” “aparticular embodiment,” and “some embodiments” may appear in variousplaces, these do not necessarily refer to the same embodiment.

The above discussion is meant to be illustrative of the principles andvarious embodiments of the present invention. Numerous variations andmodifications will become apparent to those skilled in the art once theabove disclosure is fully appreciated. For example, each sensor streamer106 may comprise multiple individual sections electrically andmechanically coupled end-to-end to form each overall streamer 106. Asanother example, although explained generally with respect to a wing ofa streamer positioning device, the antifouling cover may be adapted forany marine geophysical survey device where marine growth or build up isdesired to be reduced or avoided. It is intended that the followingclaims be interpreted to embrace all such variations and modifications.

What is claimed is:
 1. A method of deploying marine geophysical surveyequipment comprising: obtaining a disposable antifouling cover ofplastic material that, prior to installation, defines an outer surfacehaving positive image of a wing of a positioning device and defines aninterior surface having a negative image of the wing of the positioningdevice; and then installing the disposable antifouling cover of plasticmaterial on the wing of the positioning device, wherein the disposableantifouling cover occludes the wing of the positioning device; andplacing the marine geophysical survey equipment including thepositioning device in a body of water.
 2. The method of claim 1 whereinobtaining the disposable antifouling cover further comprises removingthe disposable antifouling cover from a stack of disposable antifoulingcovers where, prior to removal, the disposable antifouling cover is inan abutting relationship with at least one other disposable antifoulingcover.
 3. A method of deploying marine geophysical survey equipmentcomprising: removing a disposable antifouling cover of plastic materialfrom a stack of disposable antifouling covers where prior to removal thedisposable antifouling cover is in an abutting relationship with atleast one other disposable antifouling cover; and then installing thedisposable antifouling cover of plastic material on a wing of apositioning device, wherein the disposable antifouling cover occludesthe wing of the positioning device; and placing the marine geophysicalsurvey equipment including the positioning device in a body of water. 4.The method of claim 3 wherein removing the disposable antifouling coverfrom the stack further comprises removing the disposable antifoulingcover from a telescoping relationship with the other disposableantifouling covers.
 5. The method of claim 3 wherein installing furthercomprises at least one selected from the group consisting of: installingthe disposable antifouling cover that is pre-treated with a coatingconfigured to reduce marine growth on an exterior surface of thedisposable antifouling cover; and coating the disposable antifoulingcover with a coating configured to reduce marine growth on an exteriorsurface of the disposable antifouling cover.
 6. The method of claim 3wherein installing the disposable antifouling cover on the wing of thepositioning device further comprises latching the disposable antifoulingcover in place over the wing by way of a latching feature defined by thedisposable antifouling cover.
 7. The method of claim 3 whereininstalling the disposable antifouling cover on the wing of thepositioning device further comprises latching the disposable antifoulingcover by way of at least one selected from the group consisting of: aflange member defined by the disposable antifouling cover; a protrusiondefined on an interior surface of the disposable antifouling cover; anda ridge defined on an interior surface of the disposable antifoulingcover.
 8. The method of claim 3 further comprising, between installingthe disposable antifouling cover on the wing of the positioning deviceand placing the marine geophysical survey equipment in the water,deforming at least a portion of the disposable antifouling cover.
 9. Themethod of claim 8 wherein deforming further comprises at least oneselected from the group consisting of: heat shrinking at least a portionof the disposable antifouling cover against the wing of the positioningdevice; chemically shrinking at least a portion of the disposableantifouling cover against the wing of the positioning device; andshrinking at least a portion of the disposable antifouling cover againstthe wing of the positioning device by application of electromagneticradiation.
 10. The method of claim 3 wherein installing furthercomprises installing a cover system comprising a first disposableantifouling cover within a second disposable antifouling cover.
 11. Themethod of claim 10 further comprising: exposing the first disposableantifouling cover to the water; and then removing the first disposableantifouling cover from the wing of the positioning device, the removingexposing the second disposable antifouling cover; and then exposing thesecond disposable antifouling cover to the water.
 12. The method ofclaim 3 wherein removing the disposable antifouling cover from the stackfurther comprises removing the disposable antifouling cover from atelescoping relationship with the other disposable antifouling covers.13. A method of retrieving marine geophysical survey equipment in theform a sensor streamer comprising a positioning device with a wing, thewing covered by a disposable antifouling cover prior to the retrieving,the method comprising: extracting the marine geophysical surveyequipment from a body of water; and removing the disposable antifoulingcover from the wing of the positioning device, wherein after beingremoved the disposable antifouling cover defines an outer surface havinga positive image of a wing of a positioning device and defines aninterior surface having a negative image of the wing of the positioningdevice.
 14. The method of claim 13 wherein removing the disposableantifouling cover further comprises at least one selected from the groupconsisting of: removing the disposable antifouling cover once theportion of the positioning device is on a deck of a vessel performingthe retrieving; and removing the disposable antifouling cover with thepositioning device in the water, the removing from a work boat distinctfrom a vessel onto which the marine geophysical survey equipment isretrieved.
 15. The method of claim 14 wherein removing the disposableantifouling cover further comprises removing the disposable antifoulingcover to expose an underlying disposable antifouling cover.
 16. Themethod of claim 13 wherein removing the disposable antifouling coverfrom the wing of the positioning device further comprises at least oneselected from the group consisting of: dislodging a protrusion definedon an interior surface of the disposable antifouling cover from anindention defined on an outer surface of the wing of the positioningdevice; and dislodging a ridge defined on an interior surface of thedisposable antifouling cover from a valley defined on an outer surfaceof the wing of the positioning device.